Exposure to biological maternal sounds improves cardiorespiratory regulation in extremely preterm infants

Objective: Preterm infants experience frequent cardiorespiratory events (CREs) including multiple episodes of apnea and bradycardia per day. This physiological instability is due to their immature autonomic nervous system and limited capacity for self-regulation. This study examined whether systematic exposure to maternal sounds can reduce the frequency of CREs in NICU infants. Methods: Fourteen preterm infants (26-32 weeks gestation) served as their own controls as we measured the frequency of adverse CREs during exposure to either Maternal Sound Stimulation (MSS) or Routine Hospital Sounds (RHS). MSS consisted of maternal voice and heartbeat sounds recorded individually for each infant. MSS was provided four times per 24-h period via a micro audio system installed in the infant's bed. Frequency of adverse CREs was determined based on monitor data and bedside documentation. Results: There was an overall decreasing trend in CREs with age. Lower frequency of CREs was observed during exposure to MSS versus RHS. This effect was significantly evident in infants >= 33 weeks gestation (p = 0.03), suggesting an effective therapeutic window for MSS when the infant's auditory brain development is most intact. Conclusion: This study provides preliminary evidence for short-term improvements in the physiological stability of NICU infants using MSS. Future studies are needed to investigate the potential of this non-pharmacological approach and its clinical relevance to the treatment of apnea of prematurity.